Mobile telephony is rapidly becoming a wide spread mobile technology. The technological possibilities for context-aware features are increasing, although only few services exist in real consumer settings. In an exploratory case study of high level mobile telephone users, the context measures that are relevant to mobile telephony are studied. Starting with three measures, location, time and identity, a fourth context measure is also found, leading to the measure of social situation to be important to users as well. The study concludes that the use of mobile telephony is highly influenced by this limited set of context measures but that these are not necessarily the same as the users wish to see facilitated by technology. It also suggests that when developing contextaware features for mobile communication, supporting these four pieces of information should be prioritized.